Medical Imaging System and Method with Separate Primary and Scattered Components

ABSTRACT

A computed tomography (CT) or ultra sound imaging system and method are configured to construct images of an object. The imaging system includes: a radiation or ultrasound source including a collimating or a blocking device configured to generate both a narrow beam and a wide beam; a detector configured to detect radiation or ultrasound wave from the radiation or ultrasound wave from the radiation or ultrasound source; and at least one processing circuit configured to: determine a scatter-to-primary ratio (SPR) of the wide beam based on the narrow beam; determine a primary component of the wide beam based on the SPR to thereby separate the primary component from a scattered component of the wide beam; and construct an image of an object inside a patient using the primary component to thereby improve a contrast of the object.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 13/565,819, filed Aug. 3, 2012, which is acontinuation of U.S. patent application Ser. No. 12/067,383 (now U.S.Pat. No. 8,238,513), filed Mar. 19, 2008, which is a national stage ofPCT/US2006/036550, filed Sep. 19, 2006, which claims priority to U.S.Provisional Application No. 60/596,348, filed Sep. 19, 2005. Thedisclosures of these applications are hereby incorporated by referencein their entirety.

BACKGROUND

Radiations, such as X-ray, gamma rays, infrared and visible light, aswell as mechanical waves such as sonic and ultrasonic waves have beenused to probe internal structures of an object. Radiography,mammographic imaging, ultrasound, Computed Tomography (CT), PositronEmitting Tomography (PET), and Magnetic Resonance Imaging (MRI) havebeen used widely for medical diagnostic purposes, in industrialmeasurements, security checks, and other areas.

SUMMARY

In an aspect, a computed tomography (CT) or ultra sound imaging systemis provided including: a radiation or ultrasound source including acollimating or a blocking device configured to generate both a narrowbeam and a wide beam; a detector configured to detect radiation orultrasound wave from the radiation or ultrasound wave from the radiationor ultrasound source; and at least one processing circuit configured to:determine a scatter-to-primary ratio (SPR) of the wide beam based on thenarrow beam; determine a primary component of the wide beam based on theSPR to thereby separate the primary component from a scattered componentof the wide beam; and construct an image of an object inside a patientusing the primary component to thereby improve a contrast of the object.

In some implementations, the object comprises a foreign object, and theforeign object comprises at least one of: a needle, a catheter, a dye, adrug, a therapeutic agent, or a diagnostic agent.

In some implementations, the detector is configured to move along a pathof the narrow beam to thereby measure a radiation level at a pluralityof positions along the direction to facilitate the determining of theSPR.

In some implementations, the detector comprises a plurality of detectionelements disposed at a plurality of positions along a path of the narrowbeam to facilitate the determining of the SPR.

In some implementations, the imaging system further includes at leastone of: a needle, a catheter, a dye, a drug, a therapeutic agent, or adiagnostic agent for insertion and/or injection into the patient.

In some implementations, the at least one processing circuit isconfigured to use an analytical pencil beam model, and predict theprimary component of the wide beam using the narrow beam based on theanalytical pencil beam model.

In some implementations, the at least one processing circuit isconfigured to use a Monte Carlo algorithm, and predict the primarycomponent of the wide beam.

In some implementations, the at least one processing circuit isconfigured to perform an iteration of an output image, wherein theoutput image is used as an input density map to the Monte Carloalgorithm, to generate a more accurate density map image.

In some implementations, the imaging system further includes a timingdevice configured to turn on a detecting element for a short period suchthat the detecting element detects only the primary component.

In some implementations, the detector is configured to selectively readan output from a selected detecting element to thereby separate theprimary and scattered components.

In some implementations, the at least one processing circuit isconfigured to generate an image of the object based on the scatteredcomponent.

In another aspect, an image reconstruction method is provided forComputed Tomography (CT) or ultrasound imaging, the method including:determining a scatter-to-primary ratio (SPR) of a wide beam based on anarrow beam; determining a primary component of the wide beam based onthe SPR to thereby separate the primary component from a scatteredcomponent of the wide beam; and constructing an image of an objectinside a patient using the primary component.

In some implementations, the method further includes: using a first setof CT or ultrasound images without separating the primary and scatteredcomponents as input density maps to a computer model; constructing asecond set of CT or ultrasound images based on the primary componentusing the computer model; and iterating the above operations to obtainCT or ultrasound images with improved contrast of the object.

In some implementations, the computer model comprises at least one of ananalytical equation of an SPR as a function of a position andattenuation properties of a material along a beam path, or a Monte Carloalgorithm.

In some implementations, the method further includes coordinating anemitting time from a radiation or ultrasound source and a detecting timeof a detecting element, to facilitate separation of the primarycomponent and the scattered component of the wide beam.

In some implementations, the method further includes turning on adetecting element for a short period such that the detecting elementdetects substantially only the primary component.

In some implementations, the object comprises a foreign object, whereinthe foreign object comprises at least one of: a needle, a catheter, adye, a drug, a therapeutic agent, or a diagnostic agent, wherein theimproved contrast of the object is a contrast against a background,wherein the background comprises at least one of tissue, blood, bloodvessels, bones, or body fluid, and the method further comprises: basedon the reconstructed image, at least one of: guiding tracheal intubationto thereby enhance anesthesia safety; guiding epidural puncture; guidingselective dorsal root ganglion radiofrequency treatment of postherpeticneuralgia; treating trigeminal neuralgia with CT-guided and/orultrasound-guided percutaneous foramen ovale blocking; observing changesof atelectasis after general anesthesia; or positioning an obstetrics orsurgical tool.

In another aspect, a non-transitory computer-readable medium is providedhaving instructions stored thereon, the instructions including:transmitting a narrow beam of radiation or ultrasound wave through anobject onto a detector array; transmitting a wide beam of radiationthrough the object onto the detector array; recording signal strengthsat a plurality of positions along a path of the narrow beam using thedetector array; calculating a scatter-to-primary ratio (SPR), using acomputer model, as a function of position; separating primary andscattered components of the wide beam based on the calculated SPR;constructing a first set of images using the primary component;constructing a second set of images using the scattered component; anddetermining a position of the object based on the first and second setof images.

In some implementations, the computer model comprises ananalytically-derived formula describing the SPR as a function ofpositions and attenuation properties of material along a path of thenarrow beam.

In some implementations, the computer model comprises aMonte-Carlo-derived numerical relationship describing the SPR as afunction of positions and attenuation properties of material along thepath of the narrow beam, and wherein the computer model furthercomprises predetermined scattering characteristics of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an effect of scatteredradiation or ultrasound wave in CT or ultrasound imaging.

FIG. 2 is a plot illustrating that a total dose for a 0.5 cm, 140 keVX-ray beam in an object follows closely the primary dose of a 10 cm, 140keV X-ray beam in the same object toward the same direction.

FIG. 3 is a schematic diagram illustrating an example configuration of aCT or ultrasound system utilizing a pencil beam (or a fan beam) and acone beam.

FIG. 4 is a diagram illustrating a primary-to-scatter ratio as apredictable quantity over a longitudinal distance through a medium of anobject.

FIG. 5 is a schematic diagram illustrating an example configuration ofusing two layers of X-ray detectors for a same cone beam.

FIG. 6 is a flowchart illustrating an example method of improving animage quality by iterating image reconstruction using a primarycomponent of radiation or ultrasound wave.

DETAILED DESCRIPTION

Various embodiments are described in detail below with reference to thedrawings. Like reference numbers may be used to denote like partsthroughout the figures.

When a beam of radiation or wave interacts with an internal structure ofan object, a portion of the beam may be absorbed, and a portion may bescattered. The un-scattered portion of the beam, e.g., the primaryradiation, traces more accurately the attenuation coefficient of theinternal structure as compared with the scattered radiation.

Earlier generations of Computed Tomography (CT) use narrow beams or fanbeams of X-rays, which suffer little from effects of scattered x-rayphotons. Newer generations of CT systems use cone-beam x-rays, with afield size in the order of, for example, 10 cm. Flat-panel detectorarrays may be used to reconstruct an attenuation map of an object (e.g.,a patient). Such a setup may have advantages over traditional CTs thatutilize narrow-beams or fan-beams. For example, the cone-beam CT may befaster and may achieve a more uniform resolution in a 3-D space.

However, as a result of the wide field at the target, cone-beamed x-raybeams may be associated with a large amount of scattered radiations thattend to blur the reconstructed images, wherein the images may bereconstructed based on the radiations absorbed by the detectors. In alow-energy range (˜100 keV) of x-ray photons involved in diagnosticimaging, a scatter-to-primary ratio (SPR) may be on the order of 1, ascompared to megavoltage x-rays, wherein typical SPR may be on the orderof 0.1 or smaller.

It has been shown in measurements that scattered radiations may degradethe contrast-to-noise ratio (CNR) by a factor of 2 in a cone-beam CT.There may also be shading artifacts caused by scattered radiations.However, the benefits of volumetric (e.g., cone-beam) imaging warrantthe effort to reduce scatter rather than going back to 2-D (fan-beam) or1-D (pencil beam) imaging.

Swindell and Evans (Med. Phys., vol. 23, p. 63, 1996) have computed thatthe central axis SPR is almost linear with the beam area, and is alsoalmost linear with depth in water for a 6 MV beam.

Bjarngard and Petti (Phys. Med. Biol. Vol. 33, p. 21, 1988) discoveredthat SPR(r,d), as a function of radius r and depth d, is a linearfunction of z:

SPR(r,d)=Kμz,   (1)

where μ is the linear attenuation coefficient for primary photons, andz=rd/(r+d), and K is a coefficient that may depend on the attenuationcoefficient μ. Nizin (Med. Phys. Vol. 18, p. 153) has used Eq. (1) toseparate primary and scattered radiations in the case of a Co-60 beam inwater.

Reducing “contaminations” from scattered radiations may be achievedusing grids in front of detectors. In an article “The Influence ofAntiscatter Grids on Soft-Tissue Detectability in Cone-Beam ComputedTomography with Flat-panel Detectors” by Siewerdsen et al. (Med. Phys.,vol. 31, p. 3506, 2004), it was demonstrated that the grids may filterout a portion of the scattered radiation.

However, the usefulness of the grids may be based on an assumption thatmost of the scattered photons are in directions different from those ofprimary photons. Similar methods of separating scattered radiation fromprimary radiation may have been attempted over a thousand year ago. Thatis, separating primary from scattered radiations using grids in front ofdetectors may be analogous to the attempt of viewing stars through along tube during daytime. While some limited success has been achievedusing this approach, its limitation is obvious in that the scattered day(solar) light usually still dominates the primary (direct) light fromthe stars even in that narrow cone.

Endo et al. (Med. Phys. Vol. 28, p. 469, 2001) studied the effect ofscattered radiations on image noise in cone-beam CT, and theeffectiveness of a focused collimator or a grid in reducing the noise.

Separating primary and scattered radiations in CT imaging may alsoimprove the usefulness of information conveyed by scattered photons inan x-ray inspection system (Mario, Arthur W. et al., U.S. PatentApplication Pub. No. 20050089140, “Tomographic scanning x-ray inspectionsystem using transmitted and Compton scattered radiation”).

Mathematical models of separating primary and scattered radiations mayhave been explored in the field of megavoltage x-ray radiation therapyas an approach to research the different properties and behaviors of theprimary component and the scattered component (e.g., P. S. Nizin,“Electronic equilibrium and primary dose in collimated photon beams”,Med. Phys., 20, 1721-1729 (1993); P. S. Nizin, “Geometrical aspects ofscatter-to-primary ratio and primary dose”, Med. Phys., vol. 18, p. 153,1991). However, in the field of radiation therapy, such approaches aremerely research tools to improve the understanding of the physicalprocess in an object, and may not be applied to linear accelerators tophysically separate the primary and the scatter components.

FIG. 1 illustrates an example CT or ultrasound system. X-ray orultrasound wave source 1 may emit a primary beam 2, which may passthrough an object (such as a patient) 3. Attenuation and scattering maybe associated with the radiation or ultrasound wave passing through atleast a portion of the object. Scattered radiation or ultrasound wave 4,traveling in the same direction or in a direction different from that ofthe primary radiation/wave, may also reach the flat panel detector array5. A detector element 6 may receive both the attenuated primaryradiation/wave and the scattered radiation/wave.

FIG. 2 illustrates Monte Carlo simulation results using methods of thedisclosed implementations. Doses vs. depth in a patient are shown for140 kV x-ray beams through an object. The total dose of a narrow (0.5cm×0.5 cm) beam may follow closely of the primary dose of a cone beam(10 cm×10 cm at a position of 40 cm inside the patient). As such, theprimary radiation of a cone beam may be simulated using a narrow beamaccording to embodiments disclosed herein. A simulation of a fan beammay produce similar results, i.e., the scattered radiation in a fan beammay also be very small.

Based on the results illustrated in FIG. 2, in accordance with some ofthe disclosed embodiments, a multi-leaf collimator 7 may be placed infront of the x-ray source 1 as illustrated FIG. 3. The collimator 7 mayhave a variable opening 8, which may be a small squared hole, a slit, orhave any other shapes. The opening 8 may be smaller than the cone-beamitself.

In accordance with some embodiments, narrow (e.g., with a lateral spanor diameter of 0.5 cm or smaller) x-ray beams may be obtained using theabove-mentioned collimator, and may serve as probes to determine orpredict the primary component in the cone beam. Similar collimators orblocking devices may be used to obtain wide and narrow beams ofultrasound waves as well.

According to some of the disclosed implementations, a detector recordinga dose/signal level in the path of the cone beam may send the measureddose information to a computer. The computer can calculate the primarydose/signal level, based on the measured dose/signal level and theknowledge obtained from the narrow beams.

The time and exposure spent on the small beams is not necessarilywasted, nor is the patient exposed more x-ray radiation without theadvantages of an improved image. In some of the disclosedimplementations, signals from the narrow beams and the cone beams may becombined, and the final signal-to-noise ratio (SNR) may still beproportional to the total radiation exposure, including the radiationexposures from both the narrow beams and the cone beam.

Blocking devices other than the multi-leaf collimator may be used toobtain the narrow and wide beams. For example, wedges, metal blocks, orradiation/ultrasound source shutters may be used as part of a blockingdevice. The narrow beam may be a pencil beam or a fan beam, or may haveother shapes.

In some implementations, detector elements other than the detectorelement 6 may also be turned “on” to read the scatteredradiations/waves. The scattered radiations/waves may then be used topredict the strength of the scattering. Such information may be input toan image reconstruction algorithm according to some of the disclosedembodiments.

In some implementations, a slit may be used instead of the small hole.The slit may effectively produce a fan beam, the dose of which may beused to separate the primary and scattered radiations/waves of the conebeam. All the signals recorded by the detectors may be combined to avoidwasting the radiation (exposure to the patient) or time.

In some implementations, a combination of narrow beam (e.g., fan-beam)CT and wide beam (e.g., cone-beam) CT technologies may be employed. Forexample, during CT scans, an object (e.g., patient) may be exposed firstto narrow (e.g., fan) beams, and then to wide (e.g., cone) beams.Alternatively, the object may be exposed first to wide beams, and thento fan beam.

The signals read off the detectors during the wide beam exposures may beassociated with the total dose or signal levels at the detectors. Such atotal dose/signal level may be separated into primary and scattercomponents based on detector readout obtained from the narrow-beamexposures. The signals may be combined, and the primary dose/signal maybe used to reconstruct a first set of CT or ultrasound images, and thedose/signal level from the scattered radiation/wave may be used toreconstruct a separate set of CT/ultrasound images corresponding toscattered radiation/waves.

FIG. 4 illustrates a total dose of a cone beam inside an object (whichmay have an arbitrary geometry) with a known attenuation map. Theprimary and scattered doses may be separated from the total dose, forexample, based on Equation (1).

In an example, if a detector is placed at a position A and anotherdetector is placed at a position B, and if the attenuation properties ofmaterials along the beam path between locations A and B are known, thenbased on Equation (1), the SPR can be derived. Using the readout of thetotal doses from point A and point B, separate primary and scatter dosescan be derived based on the total doses and the SPR. This principle maybe further illustrated in an example shown in FIG. 5.

FIG. 5 illustrates, according to some implementations, that a flat-panelx-ray detector array 5 may be supplemented with a second detector array9. The detector system according to the illustrated implementationincludes two-layer detector arrays 5 and 9. The two array 5 and 9 may beflat panels, and may be separated by a known distance. One or morematerials having known attenuation and scattering properties may fill aspace between the two arrays.

The SPR, as a function of relative positions of detector element 6 anddetector element 10, may be derived based on Monte Carlo simulationsaccording to some implementations, or based on analytical solutions suchas Equation (1) according to some implementations. The SPR may depend onthe distance between the two layers, relative positions of detectorelements, and the properties of the filling material(s). During a CTprocedure, both layers may record different dosages at the substantiallysame time, and a primary dose may be derived based on the two dosagesrecorded by the two layers of detectors.

The filling material between the two layers may have measurable or knownattenuation properties. Examples of such materials include, but are notlimited to, air, water, plastic, solid water, rubber, etc.

According to some implementations, the effect of the two layers mayalternatively be achieved using only one layer. This single layer mayhave its position moved along the beam direction, or against the beamdirection, for example, from one exposure to another exposure. Such arecording of dose-distance relationship may allow the separation ofprimary and scatter using Monte Carlo simulations, or algorithmsdescribed in Equation (1) and alike. In some other implementations, themotion of the detector array may be replaced with, or supplemented by,moving the x-ray source 1.

In some other implementations, the detector arrays may alternatively beimplemented using volumetric detector arrays, which may record aradiation dosage distribution in 3-D.

In some implementations, the individual detector elements in thetwo-layer detector array, or in the volumetric detector array, may bearranged such that they do not shadow each other in the beam. In someimplementations, shadowing may be allowed, and algorithms may beimplemented to take into account the shadowing based on the detectors'attenuation coefficients. The SPR can still be obtained in thisapproach.

In some implementations, the CT images reconstructed from a conventionalCT method may be used as input to Monte Carlo simulations. The MonteCarlo simulations may track the photons and label them as primary orscattered photons. Through the Monte Carlo simulations, the fractions ofprimary and scattered components of the photons received by eachdetector may be determined, and a new set of images may be reconstructedusing only the primary component. Iterations can be employed to obtainimproved images.

In addition to obtaining a first set of images based on the primaryradiation, a second set of images may also be obtained based onscattered radiations. This may be achieved, for example, by comparingthe primary with the total radiations. The first set of images maycontain the most accurate density/attenuation information of theinternal structure of the object, and the second set of images mayprovide additional information that is also of diagnostic interests.

By separating the scattered component from the primary componentaccording to implementations disclosed herein, the object density mapmay be generated with a much higher accuracy. This may be due to that,for example, the primary component may respond to the density variationin a more predictable way as compared with the scattered component, andthe scattered component may tend to degrade the image quality. Byreconstructing a patient attenuation coefficient map based on primaryradiation only, the density of the patient's tissues may bequantitatively analyzed from the re-constructed CT image.

In some implementations, the mathematical approaches to separate primaryand scattered radiations may be realized using computer algorithms. Suchalgorithms may be constructed based on the properties and behaviors ofthe primary and scatter components of x-ray radiations.

The properties and behaviors of the primary and scatter components ofx-ray radiations may include, for example, that the primary componentand the scattered component behave differently as the beam sizeincreases. For example, as the beam size increases, the percentage ofthe primary component relative to the total dose may decrease.

In another example, at small fields (e.g., <0.5 cm in diameter), all thedoses deposited in tissues may be mostly primary doses. Such a propertymay be used, according to some of the disclosed implementations and asdemonstrated in the FIG. 2, to separate the primary component from thescattered component of an x-ray radiation. In an example, the x-rayradiation may be in an energy of about 140 keV, typical for thediagnostic imaging purposes.

In another example, the properties and behaviors of the primary andscatter components of x-ray radiations used to design algorithmsaccording to some of the disclosed implementations may include that theprimary component and the scattered component behave differently as thedistance from the x-ray source increases. In the case of diagnosticx-ray, Equation (1) may be used to quantitatively represent one of suchbehaviors according to some of the implementations disclosed herein.

In yet another example, the primary component and the scatteredcomponent react differently to material (e.g., tissue) densityvariations when transporting through the material (e.g., tissue). Suchdifferent behaviors may be described (e.g., implicitly) in equationsdominating Monte Carlo simulations of radiation transport. For example,each individual photon may be traced, and the primary and scatteredcomponents may be labeled within the Monte Carlo simulations. The finalsimulation results may be associated with the measured quantities.

An example method of obtaining an improved CT or ultrasound image inaccordance with some implementations is summarized in FIG. 6. An inputimage, such as a conventional image without separating the primary andscattered components, may be first obtained in the step 61. The inputimage may be input to a mathematical model in the step 62. Themathematical model may include, for example, an analytical equationsimilar to Equation (1), and/or may include a Monte Carlo algorithm.

Using the mathematical model, separation of primary and scatteredradiation components may be realized in step 63. An image may besubsequently reconstructed based on the primary radiation component instep 64.

If the quality of the reconstructed image is deemed unsatisfactory inthe step 65, the reconstructed image may be input to the mathematicalmodel. Some of the steps may be iterated, for example, starting with thestep 62.

If the quality of the reconstructed image is considered satisfactory,the reconstructed image may be output for practical use. A separateimage constructed based solely on the scattered radiation may optionallybe generated, as the scattered radiation may also contain usefulinformation.

Many medical tools are made with metals or made with plastic (such ascatheters), these materials have scattering properties very differentfrom those of tissues. As such, in situ imaging with the imaging systemand method of the invention may have higher accuracy, improved contrast,and require less radiation dose. For example, catheter positioning canbe achieved with higher accuracy with a lower radiation dose. Theadvantages of separating primary and scattered radiations may be moreapparent for foreign objects (e.g., needles, catheters, dyes, drugs,therapeutic and/or diagnostic agents, etc.) inside patents' issues orblood vessels. For example, by constructing the images using only theprimary radiation, or constructing separate images respectively from theprimary and scattered radiations, the contrast of the foreign objectagainst its background (e.g., tissue, blood, blood vessels, bones, bodyfluid, etc.) can be significantly improved.

In some embodiments, CT and/or ultrasound scan of cervical regions andtrachea reconstruction in patients with tracheal stenosis are used toguide tracheal intubation and enhance the anesthesia safety. In someembodiments, CT and/or ultrasound scan are used to guide difficultepidural puncture. In some embodiments, CT-guided and/orultrasound-guided selective dorsal root ganglion radiofrequencytreatment of postherpetic neuralgia is employed. In some embodiments,CT-guided and/or ultrasound-guided percutaneous foramen ovale blockingare employed to treat trigeminal neuralgia. In some embodiments, CTand/or ultrasound scan are employed to observe the changes ofatelectasis after general anesthesia.

In at least some of these embodiments, separation of the primary andscattered radiations in the CT scans and/or separation of the primaryand scattered ultrasound waves are performed according to the methodsdescribed above. In particular, higher contrast and improved positioningaccuracy can be achieved through the images obtained from primaryradiation/wave, and/or obtained respectively from primary and scatteredradiations/waves. Metal, plastic, or other materials used for the toolsin anesthesia, obstetrics, as well as surgical tools may have distinctscattering characteristics for x-rays and/or ultrasound waves. As such,positioning of these tools can be more accurately achieved with a muchlower radiation dose to the patient as compared with imaging withoutseparating the primary and scattered radiations/waves. In someembodiments, separation of primary and scattered radiations/wave isemployed to better observe agents such as anesthesia fluid and drugsthrough the catheters. These agents may also have distinct scatteringcharacteristics.

The distinct scattering characteristics may be predetermined, and storedin a memory device and be part of a computer model. By using thepredetermined scattering characteristics, the foreign object (such asthe needle, catheter, or agents) may be quickly and more accuratelyidentified with minimal radiation or ultrasound wave level.

Advantages of one or more embodiments disclosed herein may include, butare not limited to improved image quality with more accurate informationof an internal structure based on primary radiation; optional imagesobtained from scattered radiations providing more useful information;achievable by incorporating algorithms into, or by replacing detectorarrays of, existing imaging systems.

All references cited in the description are hereby incorporated byreference in their entirety. While the disclosure has been describedwith respect to a limited number of embodiments, those skilled in theart, having benefit of this disclosure, will appreciate that otherembodiments can be advised and achieved which do not depart from thescope of the description as disclosed herein.

1. A computed tomography (CT) or ultra sound imaging system comprising:a radiation or ultrasound source including a collimating or a blockingdevice configured to generate both a narrow beam and a wide beam; adetector configured to detect radiation or ultrasound wave from theradiation or ultrasound wave from the radiation or ultrasound source;and at least one processing circuit configured to: determine ascatter-to-primary ratio (SPR) of the wide beam based on the narrowbeam; determine a primary component of the wide beam based on the SPR tothereby separate the primary component from a scattered component of thewide beam; and construct an image of an object inside a patient usingthe primary component to thereby improve a contrast of the object. 2.The imaging system of claim 1, wherein the object comprises a foreignobject, and wherein the foreign object comprises at least one of: aneedle, a catheter, a dye, a drug, a therapeutic agent, or a diagnosticagent.
 3. The imaging system of claim 2, wherein the detector isconfigured to move along a path of the narrow beam to thereby measure aradiation level at a plurality of positions along the direction tofacilitate the determining of the SPR.
 4. The imaging system of claim 2,wherein the detector comprises a plurality of detection elementsdisposed at a plurality of positions along a path of the narrow beam tofacilitate the determining of the SPR.
 5. The imaging system of claim 4,further comprising at least one of: a needle, a catheter, a dye, a drug,a therapeutic agent, or a diagnostic agent for insertion and/orinjection into the patient.
 6. The imaging system of claim 1, whereinthe at least one processing circuit is configured to use an analyticalpencil beam model, and predict the primary component of the wide beamusing the narrow beam based on the analytical pencil beam model.
 7. Theimaging system of claim 1, wherein the at least one processing circuitis configured to use a Monte Carlo algorithm, and predict the primarycomponent of the wide beam.
 8. The imaging system of claim 7, whereinthe at least one processing circuit is configured to perform aniteration of an output image, wherein the output image is used as aninput density map to the Monte Carlo algorithm, to generate a moreaccurate density map image.
 9. The imaging system of claim 1, furthercomprising a timing device configured to turn on a detecting element fora short period such that the detecting element detects only the primarycomponent.
 10. The imaging system of claim 1, wherein the detector isconfigured to selectively read an output from a selected detectingelement to thereby separate the primary and scattered components. 11.The imaging system of claim 1, wherein the at least one processingcircuit is configured to generate an image of the object based on thescattered component.
 12. An image reconstruction method for ComputedTomography (CT) or ultrasound imaging, the method comprising:determining a scatter-to-primary ratio (SPR) of a wide beam based on anarrow beam; determining a primary component of the wide beam based onthe SPR to thereby separate the primary component from a scatteredcomponent of the wide beam; and constructing an image of an objectinside a patient using the primary component.
 13. The method of claim12, further comprising: using a first set of CT or ultrasound imageswithout separating the primary and scattered components as input densitymaps to a computer model; constructing a second set of CT or ultrasoundimages based on the primary component using the computer model; anditerating the above operations to obtain CT or ultrasound images withimproved contrast of the object.
 14. The method of claim 13, wherein thecomputer model comprises at least one of an analytical equation of anSPR as a function of a position and attenuation properties of a materialalong a beam path, or a Monte Carlo algorithm.
 15. The method of claim12, further comprising coordinating an emitting time from a radiation orultrasound source and a detecting time of a detecting element, tofacilitate separation of the primary component and the scatteredcomponent of the wide beam.
 16. The method of claim 12, furthercomprising turning on a detecting element for a short period such thatthe detecting element detects substantially only the primary component.17. The method of claim 12, wherein the object comprises a foreignobject, wherein the foreign object comprises at least one of: a needle,a catheter, a dye, a drug, a therapeutic agent, or a diagnostic agent,wherein the improved contrast of the object is a contrast against abackground, wherein the background comprises at least one of tissue,blood, blood vessels, bones, or body fluid, and the method furthercomprises: based on the reconstructed image, at least one of: guidingtracheal intubation to thereby enhance anesthesia safety; guidingepidural puncture; guiding selective dorsal root ganglion radiofrequencytreatment of postherpetic neuralgia; treating trigeminal neuralgia withCT-guided and/or ultrasound-guided percutaneous foramen ovale blocking;observing changes of atelectasis after general anesthesia; orpositioning an obstetrics or surgical tool.
 18. A non-transitorycomputer-readable medium having instructions stored thereon, theinstructions comprising: transmitting a narrow beam of radiation orultrasound wave through an object onto a detector array; transmitting awide beam of radiation through the object onto the detector array;recording signal strengths at a plurality of positions along a path ofthe narrow beam using the detector array; calculating ascatter-to-primary ratio (SPR), using a computer model, as a function ofposition; separating primary and scattered components of the wide beambased on the calculated SPR; constructing a first set of images usingthe primary component; constructing a second set of images using thescattered component; and determining a position of the object based onthe first and second set of images.
 19. The non-transitorycomputer-readable medium of claim 18, wherein the computer modelcomprises an analytically-derived formula describing the SPR as afunction of positions and attenuation properties of material along apath of the narrow beam.
 20. The non-transitory computer-readable mediumof claim 18, wherein the computer model comprises a Monte-Carlo-derivednumerical relationship describing the SPR as a function of positions andattenuation properties of material along the path of the narrow beam,and wherein the computer model further comprises predeterminedscattering characteristics of the object.